There were only four men in the whole world who knew it all. There was Lord Leighton, the most brilliant and the most eccentric scientific brain in Great Britain. The giant computer was his creation, and in a sense Dimension X was his discovery. It had been his idea to wire Richard Blade into the computer for the first time. He thought the combination of a human and an electronic brain would produce something new and unique.

It certainly had. When Blade returned from his first trip into Dimension X, it was instantly clear that he'd returned with one of the most important scientific discoveries of all time. It had to be kept a closely guarded secret, from Britain's enemies and even from her friends. It also had to be studied further.

There was a whole world-many worlds-out there in Dimension X. There were resources of knowledge, material, skills, people-a whole new British Empire that could dwarf the first one. One scientist, one computer, and one man of action wouldn't be enough for the job.

So the Prime Minister of England was told of the discovery, and several million pounds from secret funds went to establish Project Dimension X. The man called J, head of the secret intelligence agency MI6, was told, and he became the Project's administrator, security chief, and man-of-all-work. He also kept a watchful eye on Lord Leighton's more bizarre whims and fancies, particularly when they might endanger Richard Blade. J had picked Blade straight out of Oxford, seen him become MI6's crack agent, and loved the younger man as he would have loved a son.

Lord Leighton, the Prime Minister, J. Three of the four who knew the secrets of Dimension X. The fourth was Richard Blade, the man on the spot. Secret agent, natural adventurer, a man whose physical and mental gifts made him the most nearly indestructible human being alive. Veteran of twenty-six trips into Dimension X, and the only living person who could come through one alive and sane. There were doubtless others, and sooner or later they would have to be found and put to work. Meanwhile, Blade was not only indestructible, he was indispensable.